The present invention relates to a method of calibrating to a predetermined finished size vehicle wheels made of a heat-treatable aluminum sheet by means of one or more dies. As employed herein, the term "aluminum" refers to aluminum for aluminum alloys normally employed for forming wheels.
Vehicle wheels for pneumatic tires are manufactured primarily of steel and in the form of a compound unit consisting of a wheel disk and a rim. The wheel must meet certain conditions with regard to the diameter, circumference, width, depth, and alignment of the rim. After the rim has been formed by rolling, it is fitted onto the wheel disk. Usually, this is accomplished with an expansion die, or alternatively, first with an expansion die which expands the rim further than the required size, and then by compression strain, whereby the rim is pressed onto the wheel disk.
This method is less suitable for wheels made of a single piece, e.g., cast or forged aluminum wheels, especially since these wheels are already manufactured with smaller tolerances in terms of roundness compared to conventional steel wheels. Therefore, the rims of cast or forged aluminum wheels are frequently cut down to the exact circumferential dimension required to maintain the relatively close tolerances.
In the manufacture of single-piece aluminum wheels by effecting a pressing thereof, it is desirable to preserve the rim in the form in which it was pressed, that is, without cutting down to the exact circumferential dimension required. For this, cost considerations are, on the one hand, an essential criterion, but on the other hand, also much is to be said for the advantageous properties of the metal on the surface produced by pressing. Pressing results in a very uniform distribution of the worked material in the rim and in an extraordinary roundness, which means only a slight imbalance. However, subsequent heat treatment, e.g., in the form of solution heat treatment for the homogenization of the texture of the worked material, can alter the correct dimensional form, so that it is necessary not to calibrate the wheel to the desired finished size until after the solution heat treatment. Such a method is taught by U.S. Pat. No. 3,172,787 in connection with a rim having a welded seam.